Grain Boundary Engineering (GBE) refers to a family of techniques involving the processing, evaluation, and classification of grain boundaries within polycrystalline materials. Generally speaking, grain boundaries are less energetically stable than the interior regions of crystal grains. The level of instability depends upon the grain boundary type (i.e., crystallographic type), of which many exist. Certain types of grain boundaries, referred to in the art as “special” grain boundaries, exhibit improved properties compared to “general” grain boundaries. GBE may be used to manipulate or optimize the morphology and network of grain boundaries to produce a larger fraction of special grain boundaries, and hence, desirable bulk properties. The formation of annealing twins, which is a common phenomenon in various kinds of FCC metals and alloys, is thought to be a key mechanism in increasing the fraction of special boundaries.